The invention relates, generally, to blast cleaning devices and, more particularly, to a blast cleaning machine having magnetic treads for cleaning substantially vertical surfaces as well as the underside of horizontal surfaces such as are typically found on ship hulls and storage tanks.
Blast cleaning machines typically consist of a blast wheel having a plurality of blades extending radially therefrom. The blast wheel is mounted in a housing and is rotatably driven at high speed. Abrasive such as steel shot is fed onto the blades and is projected against the surface to be cleaned. The impact of the abrasive with the surface to be cleaned dislodges paint, rust and other debris from the surface. Typically, the debris is removed from the system and the spent abrasive is recirculated back to the blast wheel. The housing can either be of a stationary type into which the article to be cleaned is placed or a mobile type that is propelled over the surface to be cleaned.
One such mobile blast cleaning machine is disclosed in U.S. Pat. No. 4,377,922 issued to Bergh. While such a device performs very well on horizontal and near horizontal surfaces, it cannot clean vertical surfaces nor can it clean the underside of horizontal surfaces such as the bottom of ship hulls. A blast cleaner specifically designed for cleaning vertical surfaces is disclosed in U.S. Pat. No. 3,034,262 issued to Pawlson. The Pawlson device is a relatively small, hand-held unit that is impractical for large cleaning jobs or jobs where it is impractical or impossible for a human operator to work. Finally, U.S. Pat. No. 3,864,876, issued to Diehn, discloses a fixture for supporting a blast cleaning device fixed to a vertical surface by electromagnets.
Thus, a blast cleaner that can traverse vertical and the underside of horizontal surfaces and efficiently clean large areas is desired.